Environmental Progress - Fall 2001

IEPA Investigates Downers Grove Area Wells For TCE Contamination

Sampling of private wells shows some levels exceed federal drinking water limits.

Over the last several months, Illinois EPA sampling teams have been collecting water from private wells in the Lisle area of DuPage County. The samples were analyzed for evidence of volatile organic compounds. (Environmental Progress: Winter 2000). At that time, a metal fabrication company in Lisle was the focus of attention from the media, the public and several state agencies, due to spills of a chemical solvent that may have contaminated the private wells. The contaminant of concern in the Lisle area was trichloroethyene or TCE.

While the Illinois EPA does not typically sample and analyze private water wells, results of these tests are providing important data. The results are expected to lead to the source or sources of contamination. Individual residents are provided with the analytical results, so they can be apprised of potential health risks and advised of protective measures that may be taken.

A new contaminant - PCE - turned up later

As the investigation progressed, the Agency collected samples across I-355, into unincorporated areas of Downers Grove, to determine the extent of contamination. When investigators analyzed these findings, they discovered additional contaminants. TCE was found in some wells, but additionally they found tetrachloro- ethyene, also known as PCE, as well as other chemicals. While TCE and PCE are chemically similar, they are distinctly different chemicals and it was apparent that additional sources remained to be identified. Investiators believe that the contamination in the Downers Grove area came from a source east of I-355.

In the first round of private well sampling in Downers Grove, conducted in July 2001, approximately 160 samples taken in three areas were analyzed for levels of volatile organics. Elmore and Inverness Streets generally bound the main study area on the north, Belmont St. on the east, 59th Street on the south and Walnut St. on the west.

Some results exceeded federal drinking water standards

Of the approximately 100 samples in this area, 34 results were above the federal drinking water standards for TCE, PCE or a combination of the two. The standard is 5 parts per billion for both chemicals. Other related chemicals of concern were detected at low levels.

The second area was north of Burlington St. between Granville and Edwards Sts., and generally extended about one block. There, the chemicals of concern were not detected or sample results were well below the drinking water standard. The third area was bounded by 63rd St. on the north, Main St. on the east, 67th St. on the south and Saratoga St. on the west. Again, all samples were well below the drinking water standard or the chemicals of concern were not detected.

With this information, the Illinois EPA was able to concentrate the next round of sampling to the main area. Additional residents were contacted and the main study area was expanded to the east, which reflected the apparent direction of the contamination. In mid-September, another 170 wells were sampled. While results were still being evaluated when this publication was being finalized, 60 percent of the wells in this area show PCE or TCE contamination above the federal drinking water standards. Preparations were then made for additional sampling south and east of the main study area.

Availability session offered one-on-one talks

On October 11, 2001, Illinois EPA and other participants hosted a Public Availability Session to give the citizens of the Downers Grove area the chance to meet with officials to discuss the ongoing groundwater investigation in the area.

Representatives for the Agency for Toxic Substances and Disease Registry, the village of Downers Grove, DuPage County, Illinois Department of Public Health, the Water Quality Association of Lisle and the Illinois EPA were all available. Attendees asked the participants about the status and scope of the ongoing investigation, general and specific health issues, and the process required to become part of a public water supply.

The sessions allowed citizens to talk with representatives from the various organizations on a one-on-one basis. Results from the most recent round of private well sampling were also discussed with affected residents.

While sources of the contamination continue to be researched, there is a known history of TCE contamination in the Downers Grove area.

Under a state program to assess the presence of volatile organic compounds in groundwater, the Illinois EPA Groundwater Section sampled community water supply wells in Downers Grove in 1985 and 1986. The wells were found to be contaminated with volatile organic compounds. Measures were taken in 1987 to investigate the source of contamination and to continue monitoring the wells and the drinking water. In 1988, when the first sampling for volatile organic compounds required under the federal Safe Drinking Water Act was begun, Downers Grove did not have a drinking water standard violation. However, measures were taken to suspend use or abandon wells and in 1992 the water supply was switched to Lake Michigan water. The Illinois EPA had no information that private wells existed in the area, since the Agency is charged only with regulating public water supplies.

As the investigation continues, the Illinois EPA will continue to develop fact sheets and issue news releases as information becomes available. The Agency intends to continue the investigation until the extent of the plume of contamination is determined.